Many A&E departments have been forced to axe the NHS’s four-hour target to deal with patients, Mike Clancy, a medical expert, says. Photograph: 1exposure/Alamy

Overcrowding in hospital A&E departments in England could lead to more deaths and serious illness, MPs have been warned.

Mike Clancy, president of the College of Emergency Medicine, said there were not enough beds as more patients, many of them elderly, arrived for treatment after midnight. "If you were to look at the numbers of people multiplied by the length of time they are spending in emergency departments, that is what is increasing substantially," he told the Commons health select committee.

"You should know that is dangerous. There is mortality and morbidity associated with overcrowding, we know that …We have to get rid of that overcrowding because it is a substantial risk."

He told MPs on Tuesday many departments had dropped the NHS's four-hour target to deal with patients because of the pressure. The number of A&E patients who waited between four and 12 hours increased by 34,000, Clancy said.

The target is for hospitals to admit or discharge 95% of A&E patients within four hours. "The deterioration in four-hour performance, which is a process measure and not a quality measure, has reflected the pressure the system is under," he added.

"What has happened is that organisations are now focusing more on how many people waiting up to 12 hours, and have in a sense parked the four-hour target because it is so difficult to manage. That is a reflection of the pressure the system is under."

Patrick Cadigan, registrar of the Royal College of Physicians, said: "One of the big challenges here is out-of-hours care. And the problem is that A&E is the recognisable brand, and that's where patients will go because they know they will see someone who is expert, often within four hours, and they will receive treatment.

"Patients will go where the lights are on, and in many of these alternatives the lights are not on after five o'clock in the evening and at weekends. And we have to face up to the fact that the services, other than the A&E department, are often run on a nine to five elective basis."

Later in the Commons, the health secretary, Jeremy Hunt, again blamed Labour for the crisis, claiming the change in GP contracts in 2004, which allowed family doctors to opt out of out-of-hours care, had played a major part in causing it. He also cited Cadigan's remarks.

Hunt, who acknowledged problems with the 111 NHS advice service and said more needed to be done to give confidence in alternatives to A&E, said: "Last year's GP patient survey said that only 58% of patients know how to contact their local out-of-hours service, and said that 20% of patients find it difficult to contact their out-of-hours service, that 37% of patients feel that the service is too slow – problems that we are trying to address."

During heated exchanges, he told his Labour counterpart, Andy Burnham: "Perhaps you should visit some A&E departments, talk to some A&E consultants, talk to some doctors, talk to some nurses, because they will say to you that those changes to GPs' contracts, which you are saying have nothing to do with the pressures on A&E, have had a huge and devastating impact."